Roll doctor apparatus

ABSTRACT

Apparatus for doctoring a roll for example in a paper-making machine comprising a doctor blade support of channel form in a number of side-by-side sections for example of sheet metal, the support being pivotally mounted on a carrier projecting into the channel, and two inflatable tubes interposed between the carrier and the support for pivoting the support to cause the doctor blade to engage with or disengage from the roll. The walls of the channel are substantially continuous and cover completely the tubes and the external surfaces of the channel are provided by smooth, plane and/or curved surfaces which are devoid of ribs.

Unite States Patent 1 Winterburn et a1.

[451 July 31, 1973 1 1 ROLL DOCTOR APPARATUS [73] Assignee: JosephWinterburn Limited,

Lancaster, England 22 Filed: June 3, 1971 21 Appl.No.: 149,573

[30] Foreign Application Priority Data June 6, 1970 Great Britain27,442/70 [56] References Cited UNITED STATES PATENTS 3,611,471 Meskanenet al 15/256.51

3,564,640 2/1971 DeNoyer 15/256.51 2,498,213 2/1950 Ljungquist 151256.51FOREIGN PATENTS OR APPLICATIONS 32,443 l0/1962 Finland 15/256.51

- Primary Examiner-Leon G. Machlin Attorney-Owen, Wickerhsam & Ericksons71 ABSTRACT Apparatus for doctoring a roll for example in a papermakingmachine comprising a doctor blade support of channel form in a number ofside-by-side sections for example of sheet metal, the support beingpivotally mounted on a carrier projecting into the channel, and twoinflatable tubes interposed between the carrier and the support forpivoting the support to cause the doctor blade to engage with ordisengage from the roll. The walls of the channel are substantiallycontinuous and cover completely the tubes and the external surfaces ofthe channel are provided by smooth, plane and/or curved surfaces whichare devoid of ribs.

4 Claims, 3 Drawing Figures PATENTEB B 3. 748 686 sum 3 OF 3 Fla. '5

1 ROLL DOCTOR APPARATUS This invention relates to roll doctor apparatusfor use with a roll in, for example, a paper-making, bleaching, dyeingor printing machine.

The invention is particularly applicable to the drying rolls ofpaper-making machines and will be described in relation thereto, but itis to be understood that there is no limitation in this regard.

Two important requirements should be satisfied by roll doctor apparatusand these are as follows:

1. The apparatus should be capable of allowing for the chamber of a longroll while providing substantially uniform pressure on the roll by thedoctor blade along the length of the roll.

2. If material passes the doctor blade it must be prevented fromimpairing the proper operation of the doctor blade and/or accumulatingin such a position that it will ultimately drop off on to the web beingacted upon by the roll.

The first one of these requirements has been successfully met by theroll doctor apparatus described in the complete specification of BritishPatent No. 948.679 of D.S.T. Pattern and Engineering Co. Limited. Inthis apparatus the doctor blade is held by a number of ribbed, crankedlevers pivotally mounted in side-by-side relationship on a carrier andthese levers are biased by an inflatable tube to urge the doctor bladeagainst the roll.

However, with regard to the second requirement it has been found inpractice with the apparatus described in said specification that thereis a tendency for paper pulp which has passed the doctor blade toaccumulate in the cavities between the ribbed, cranked levers holdingthe blade. This is because as the pulp passes the doctor blade it losesits velocity and breaks up and thus has a tendency to enter anyavailable cavity such as the space between the ribs on two adjacentblade-holding levers. The pulp which accumulates in the cavitiesultimately falls off and may break the web which is being treated. Also,the cranked levers have been arranged at a wider spacing than that shownin the complete specification referred to above since it was found forstructural reasons that it was not necessary to place the levers soclose together. The pulp tends to get between the levers and theinflatable tube and there is also the danger that, when the operatorclears the machine and uses a spiked rod or stick for this purpose, hemight puncture the tube.

A third important requirement of roll doctor apparatus is that it shouldbe possible to lift the blade off the roll when the machine is idle orfor maintenance and replacement purposes.

It is an object of the present invention to provide a roll doctorapparatus which fulfils not only the first but also the secondrequirement mentioned above.

An aim of a preferred embodiment of the invention is to provide a rolldoctor apparatus which also fulfils the third requirement mentionedabove.

According to the invention there is provided a roll doctor apparatuscomprising a carrier; a flexible support (as hereinafter defined) ofgenerally channel section mounted on the carrier for pivoting about anaxis parallel to the length of the channel, an edge portion of thecarrier being received within the channel; a flexible doctor blade (ashereinafter defined) mounted on the support to project externally of thechannel and away from the carrier; and a tube which is interposedbetween the said edge portion of the carrier and a wall of the channeland is expansible by the introduction of fluid into it so as to pivotthesupport relatively to the carrier and cause the doctor blade to engagethe roll, characterised in that the walls of the channel aresubstantially continuous and overlie completely said tube and theexternal surfaces of the channel are provided by smooth surfaces whichare devoid of ribs.

By this arrangement, any pulp or other material which passes the doctorblade is not encouraged to hang on to the external surfaces of thechannel because of their shape and because of the absence of ribs whichproject from the external surfaces of the channel and which havesubstantial longitudinal extents in directions perpendicular to thepivot axis of the support, such as are provided on the cranked levers inthe apparatus described in the aforementioned complete specification.

With regard to the third requirement, that it should be possible to liftthe blade off the roll when the machine is idle or for maintenance andreplacement purposes, it may in some cases be possible to arrange the vapparatus that the blade will move under gravity out of contact with theroll surface when there is no fluid pressure in the tube. Preferably,however, means are provided for positively lifting the doctor blade offthe roll and such means comprises a second expansible tube which isinterposed between the edge portion of the carrier and a wall of thechannel and is expansible by the introduction of fluid into it so as topivot the support relatively to the carrier and cause the doctor bladeto lift from the roll. If such a tube is provided then it issubstantially covered by the wall of the channel which it engages so asto prevent it being punctured during clearing of the machine by a spikedrod or stick as described above.

If two expansible tubes are provided then they may be arranged in one oftwo manners. The tubes may be on the same side face of the carrier andon opposite sides of the pivot axis of the doctor blade support so thatboth tubes engage the same side wall of the channel of the support.Alternatively, the tubes may be mounted on opposite side faces of thecarrier so that one tube engages one side wall of the channel of thesupport and the other tube engages the other sidewall of the channel.

When we say that the support and the blade are flexible we mean thatthey are arranged so that the blade can engage the roll throughout thewhole length thereof when the blade is urged into engagement with theroll by the expansible tube or the relevant one of the expansible tubes.The blade itself will normally be in one piece except when it is usedwith a very long roll, in which case it may be in a number of sections,and will be constructed so that it can flex about axes transverse to itslength. The support may be continuous along the length of the roll andof sufficient flexibility about axes transverse to its length to enablethe blade to engage the roll throughout the length of the latter.Alternatively, the support may be in a number of sideby-side sectionspivoted to the carrier. In the latter case the sections will be arrangedside-by-side at such spacing as substantially to cover the expansibletube or tubes.

Whether the support is continuous or made in sideby-side sections it maybe made from sheet metal or from an extrusion.

The support, or each section thereof, preferably comprises a generallyZ-shaped member of sheet metal having first and second approximatelyparallel flanges separated by a web integral therewith and a thirdflange of sheet metal secured to the second flange and forming, with thefirst flange, the side walls of the channel or parts thereof, the baseof the channel or a part thereof being formed by the web. In such aconstruction it is obviously necessary to fasten the second and thirdflanges together and this may be effected by welding or other techniquesor it may be necessary to rivet together the two flanges. In this casethe rivet heads would form small projections from the otherwise smoothexternal surfaces of the channel but there would still be no ribs havingsubstantial longitudinal extents perpendicular to the pivot axis toprovide cavities in which could accumulate material from the roll beingdoctored.

Alternatively, the support or the sections thereof could be formed of anextruded section of similar shape to that obtained by securing togethera Z-shaped mem ber and said third flange as described above.

Conveniently the first or third flange of the support or each supportsection is formed with a transverse groove of curved cross section whichembraces a pivot shaft mounted on the carrier. This arrangement providesa simple pivotal mounting for the support.

Preferably the first flange or/and the third flange of the support oreach support section are shaped so that the end thereof remote from thedoctor blade is disposed nearer to the carrier than the remainder of theflange. Thus, the mouth of the channel is narrower than the channelitself so as to provide further protection for the tube or tubes againstdamage.

The carrier may have means arranged to cooperate with the support tolimit the pivotal movement of the support towards the roll.

The support will be provided with means for mounting the doctor bladeand such means may be a slot opening towards the roll to receive theblade, the slot having a base which forms an abutment for the edge ofthe blade remotefrom the roll and the blade carrying a number of springswhich are engaged in the slot to hold the blade in position.

Two embodiments of the invention will now be described in detail by wayof example with reference to the accompanying diagrammatic drawings, inwhich:

FIG. 1 is a part sectional view of roll doctor apparatus constituting afirst embodiment of the invention taken on the line II of FIG. 2;

FIG. 2 is a plan view of part of the apparatus shown in FIG. 1; and

FIG. 3 is a view similar to FIG. 1 of roll doctor apparatus constitutinga second embodiment of the invention.

The two embodiments of the invention illustrated in the drawings aresimilar in that they each comprise a base carrying two spaced bearinghousings, of which one is shown at 11, supporting between them a roll12, (for example a drying roll in a paper-making machine) for actingupon a web 13 (of paper) the ends of the roll being formed withtrunnions 14 which are received in the bearings. The web 13 is showntravelling in a horizontal path although its path could be disposed atan inclination to the horizontal. Moreover, a further roll could bedisposed beneath the roll 12 so that the web passes through the nipbetween them.

The base 10 also carries two spaced bearing housings, of which one isshown at 15, supporting between them a carrier 16 for a doctor bladesupport generally designated 17. The carrier is of angle form and haswelded to the outer face of its vertical limb two aligned square sectionbars, one of which is shown at 18, whose projecting ends are formed toprovide trunnions 19 received in the bearings of the housings 15. One ofthe trunnions 19 namely the one seen in the drawings, has keyed to it aradially extending arm 20 which is pivotally connected at its outer endto one end of a torque link 21, the other end of this link being pivotalon a fixed part of the base 10. The torque link arrangement preventspivoting of the carrier 16 about the common axis of the trunnions 19.The torque link 21 incorporates adjusting means 22 whereby thedisposition of the carrier 16 can be varied as required.

A further torque link arrangement may be provided at the opposite sideof the machine depending on the width of the latter.

Referring now to FIGS. 1 and 2 of the drawings the doctor blade support17 is generally of channel shape and the horizontal limb of the carrier16 is received in the channel. The support comprises a number ofsections 23, as shown in'FIG. 2, arranged closely side by side on thecarrier. In an alternative arrangement (not shown) the support may becontinuous along the whole length of the roll 12. Each section 23comprises a Z- section member of sheet metal having a first flange 24, aweb 25, and a second flange 26, the flanges 24 and 26 being generallyparallel to one another with the web 25 extending at right anglesthereto and forming the base of the channel. Secured to the secondflange 26 by rivets 27 is a third flange 28 of sheet metal, the twoflanges 24 and 28 forming the side walls of the channel. The flange 26is formed with a U-shaped portion 29 which provides, with the opposedportion of the flange 28, a slot which receives a doctor blade 30, thebase of the slot providing an abutment for the edge of the doctor blade30 remote from that part which engages the roll 12, and the blade beingprovided along its said edge with a series of spring clips 31 holdingthe blade in position in the slot.

The support 17 is mounted on the carrier 16 for pivoting about a pivotshaft 32 mounted between brackets 33 depending from the carrier and inthe embodiment shown the flange 24 is provided with a transverse portion34 of curved cross section which embraces the shaft 32. Screwed intoapertures in the carrier 16 are a number of bins 35 which engage inslots in the free edge portion of the flange 24 to prevent the supportmoving horizontally towards the roll 12 and to limit the pivotalmovement thereof. The arrangement may be modified by forming the freeedge portion of the flange 24 so that it hooks around the shaft 32 thusdispensing with the pins 35.

Mounted on opposite side faces of the horizontal limb of the carrier 16are two inflatable tubes 36 and 37, one tube engaging one side wall ofthe channel of the support 17 and the other tube engaging the other sidewall. The ends of the tubes are closed by two elements of which one isshown at 38, and this element has two air lines 39 (showndiagrammatically in FIG. 2) connected to it and communicating with therespective tubes. The two air lines are connected to a common source ofcompressed air 40, and each line incorporates a valve 41 for controllingthe air pressure in the associated tube.

The walls of the channel of the support 17 provided by the flanges 24and 28 substantially completely cover the inflatable tubes 36 and 37 soas to protect them from being damaged during clearing of the machine bymeans of a spiked rod or stick and to prevent material from the roll 12getting between the carrier 16 and the said flanges. It will be notedthat the flanges 24 and 28 are so shaped that their free edge portionsremote from the roll 12 are disposed nearer to the carrier than theirportions adjacent the base of the channel, the flange 28 being providedwith a cranked portion 42 for this purpose.

Furthermore, it will be seen that the external surfaces of the channelshaped support 17 formed by the flanges 24 and 28 and the web 25 aresmooth and either plane or curved and do not have any ribs on them whichhave substantial longitudinal extents perpendicular to the shaft 32. Itfollows that the cavities in which material can accumulate on thesupport are limited and there is little danger that material willaccumulate on the support and drop on to the web 13 being acted upon bythe roll 12.

The doctor blade 30 is urged into engagement with the surface of theroll 12 by introducing compressed air into the tubes 36 and 37 with agreater pressure in the tube 37 than in the tube 36 so that the tube 37expands to a greater extent. The tube 36 merely acts as a steady whenthe blade is being forced into engagement with the roll 12. The support17 must be sufficiently flexible for the blade to be able to be engagedwith the roll over the whole length of the roll and this is effectedeither by making the support in a number of sections as illustrated orby making the support continuous but of sufficient flexibility aboutaxes perpendicular to the shaft 32 to enable the blade to engage theroll throughout the length thereof.

It will be appreciated that in operation, material from the roll beingdoctored passes over the smooth upper surface of the flange 28 and onlyany material passing the doctor blade can engage the external surfacesof the web 25 and the flange 24 and due to the shape of these surfacesthere will be no tendency for the material to build up into anaccumulation on the surfaces and then drop on to the web 13 with adanger of breaking it.

By introducing a greater air pressure into the tube 36 than into thetube 37 the support 17 can be pivoted to lift the doctor blade 30 fromthe roll.

Referring now to FIG. 3, the support 17 in this embodiment is similar inconstruction to the support of the embodiment shown in FIGS. 1 and 2.Thus, the support is in a number of sections each comprising a generallyZ-shaped sheet metal member having a first flange 43, a web 44 and asecond flange 45, the web being disposed at an inclination to theparallel flanges. A third flange 46 of sheet metal is riveted to theflange 45. Riveted to the flanges 45 and 46 is a U-shaped blade support47 which provides a slot to receive a doctor blade 48, the base of theslot forming an abutment for the edge of the blade remote from the roll12 and the blade being provided with spring clips 49 to hold it in theslot. 6

The flange 43 is provided with a transverse arcuate portion 50 whichembraces a shaft 57 supported by brackets 52 on the carrier 16. Thearcuate portion 50 extends round more than 180 so that it is preventedfrom becoming disengaged from the shaft 51.

Arranged on opposite sides of the shaft 51 are two inflatable tubes 53and 54 which are interposed between one side face of the horizontal limbof the carrier 16 and one side wall of the channel of the support 17.

The tubes 53 and'54 are closed by end elements 55 and are connected to apneumatic circuit similar to that shown in FIG. 2.

Engagement of the doctor blade 48 with the roll 12 is effected byintroducing a greater air pressure into the tube 54 than into the tube53, and lifting of the blade from the roll is performed by introducing agreater air pressure into the tube 53 than into the tube 54.

It will be seen that the channel shaped support 17 whose walls areprovided by the flanges 43 and 46 and the web 44 has smooth, plane orcurved external surfaces which prevent the build up of material thereonand also that the flange 43 substantially covers both of the tubes 53and 54. The flange 46 is shaped so that its free end portion is inclinedtowards the carrier. The tubes are thus protected from accidentaldamage.

As with the embodiment of FIGS. 1 and 2, the support 17 may be formed asone continuous member'instead of being in a number of side by sidesections. In either case it will be sufficiently flexible to allow thedoctor blade to engage the roll throughout the whole length of thelatter. I

In both of the embodiments described, the parts of the support are madefrom sheet metal and are riveted together. However it is also within thescope of the-invention to make the parts in one piece as an extrusion orto fix them together by some othermeans.

It will be seen that the invention provides an improved roll doctorapparatus in which the expansible tubes are protected and in which theexternal surfaces of the blade support discourage the build up ofmaterial thereon.

In some cases, the tube serving to lift the doctor blade from the rollcan be dispensed with if the apparatus is mounted in such a positionthat the blade will become disengaged from the roll by gravity.

We claim:

1. In combination with a roll, a roll doctor apparatus comprising a. acarrier; t r

b. a flexible support of generally channel section mounted on thecarrier for pivoting relative to the latter about an axis parallel tothe length of the channel, the carrier having an edge portion which isreceived within the channel and the support comprising a generallyZ-shaped member of sheet metal which has first and second approximatelyparallel flangesseparated by a web integral therewith, and a member ofsheet metal secured to-the second flange and providing a third flangewhich forms, with the first flange, the side walls of the channel, thebase of the channel being formed by the web;

0. a flexible doctor blade mounted on the support to project externallyof the channel and away from the carrier;

cl. a tube which is interposed between the said edge portion of thecarrier and a sidewall of the channel, the walls of the channel beingsubstantially continuous and covering completely the said tube and theexternal surfaces of the channel being provided by smooth unribbedsurfaces; and

e. means for introducing fluid into the tube to expand it so as to pivotthe support relative to the carrier and cause the doctor blade to engagethe roll.

2. An apparatus as claimed in claim 1 wherein a pivot shaft is mountedon the carrier and the first flange of the generally Z-shaped member ofthe support is formed with a transverse groove of curved cross sectionwhich embraces said shaft.

3. An apparatus as claimed in claim 1 wherein at least one of theflanges defining the side walls of the channel is shaped so that the endthereof remote from the doctor blade is disposed nearer to the carrierthan the remainder of the flange.

4. In combination with a roll, a roll doctor apparatus comprising a. acarrier;

b. a mounting for the carrier;

c. a flexible support having two spaced approximately parallel flangesjoined by a web which extends approximately at right angles to saidflanges and, with the latter, forms a channel, and a further flangewhich projects from the web in a direction away from the channel, thecarrier having an edge portion which extends away from the mounting andis received within the channel;

d. pivot means between said edge portion of the carrier and said supportwhereby the latter is mounted on the carrier for pivoting relativethereto about an axis parallel to the length of the channel;

e. a flexible doctor blade mounted on said further flange of the supportand extending in a direction away from the channel;

f. a tube which is interposed between the said edge portion of thecarrier and a wall of the channel, the walls of the channel beingsubstantially continuous and overlying completely the said tube and theexternal surfaces of the channel being provided by smooth unribbedsurfaces; and

g. means for introducing fluid into the tube to expand it so as to pivotthe support relatively to the carrier and cause the doctor blade toengage the roll.

1. In combination with a roll, a roll doctor apparatus comprising a. acarrier; b. a flexible support of generally channel section mounted onthe carrier for pivoting relative to the latter about an axis parallelto the length of the channel, the carrier having an edge portion whichis received within the channel and the support comprising a generallyZ-shaped member of sheet metal which has first and second approximatelyparallel flanges separated by a web integral therewith, and a member ofsheet metal secured to the second flange and providing a third flangewhich forms, with the first flange, the side walls of the channel, thebase of the channel being formed by the web; c. a flexible doctor blademounted on the support to project externally of the channel and awayfrom the carrier; d. a tube which is interposed between the said edgeportion of the carrier and a side wall of the channel, the walls of thechannel being substantially continuous and covering completely the saidtube and the external surfaces of the channel being provided by smoothunribbed surfaces; and e. means for introducing fluid into the tube toexpand it so as to pivot the support relative to the carrier and causethe doctor blade to engage the roll.
 2. An apparatus as claimed in claim1 wherein a pivot shaft is mounted on the carrier and the first flangeof the generally Z-shaped member of the support is formed with atransverse groove of curved cross section which embraces said shaft. 3.An apparatus as claimed in claim 1 wherein at least one of the flangesdefining the side walls of the channel is shaped so that the end thereofremote from the doctor blade is disposed nearer to the carrier than theremainder of the flange.
 4. In combination with a roll, a roll doctorapparatus comprising a. a carrier; b. a mounting for the carrier; c. aflexible support having two spaced approximately parallel flanges joinedby a web which extends approximately at right angles to said flangesand, with the latter, forms a channel, and a further flange whichprojects from the web in a direction away from the channel, the carrierhaving an edge portion which extends away from the mounting and isreceived within the channel; d. pivot means between said edge portion ofthe carrier and said support whereby the latter is mounted on thecarrier for pivoting relative thereto about an axis parallel to thelength of the channel; e. a flexible doctor blade mounted on saidfurther flange of the support and extending in a direction away from thechannel; f. a tube which is interposed between the said edge portion ofthe carrier and a wall of the channel, the walls of the channel beingsubstantially continuous and overlying completely the said tube and theexternal surfaces of the channel being provided by smooth unribbedsurfaces; and g. means for introducing fluid into the tube to expand itso as to pivot the support relatively to the carrier and cause thedoctor blade to engage the roll.